The Internet of Things is a network in which various devices having specific capabilities of sensing, computation, execution, and communication are deployed to obtain information from a physical world, to implement information transmission, coordination, and processing by using a network, so as to implement interconnection between humans and things and between things and things. In brief, the Internet of Things intends to implement interconnection and interworking between humans and things and between things and things. The Internet of Things may be applied to various fields such as a smart grid, intelligent agriculture, intelligent transportation, and environmental monitoring.
The mobile communications standards organization 3rd Generation Partnership Project (3GPP) is performing technology research and standard optimization for a service in the Internet of Things. The 3rd Generation Partnership Project mainly aims at cost reduction and coverage enhancement in terms of research and optimization. For cost reduction, an important research direction may be to reduce an operating bandwidth of a terminal device, for example, limit the operating bandwidth of the terminal device to 1.4 MHz (or 200 KHz, or 180 KHz). For coverage enhancement, coverage enhancement support is mainly provided for a machine type communication (MTC) device in a basement, or the like, that has a relatively large path loss, so that the device in the special scenario can access a network to obtain a service. Coverage enhancement intends to provide coverage enhancement support for user equipment in a basement or on a cell edge and with a relatively large path loss, so that the user equipment in the scenario can access a network to obtain a service. Coverage enhancement may be one or more of repeated transmission, spread spectrum transmission, retransmission, time interval bundling transmission, narrowband (such as subcarrier scheduling) transmission, ultra-narrowband (such as a narrowband with a bandwidth of tens of hertz to ten-odd kilohertz) transmission, power spectrum density boosting transmission, relaxed-requirement transmission, or continuous-attempt transmission. Signal repetition is one of methods for implementing coverage enhancement. In coverage enhancement, coverage can be extended to some extent, but more system resources may be consumed. Therefore, it is necessary to improve resource usage when coverage enhancement is implemented by means of signal repetition.
A base station sends a physical downlink control channel (PDCCH) to user equipment (UE). The UE sends a physical uplink shared channel (PUSCH) to the base station according to the PDCCH. The base station receives the PUSCH sent by the UE. Then, the base station sends a hybrid automatic repeat request (HARQ) feedback to the UE according to a PUSCH receiving status. For example, the HARQ feedback may be a state of acknowledgement (ACK) or negative acknowledgement (NACK). For a HARQ feedback currently implemented on a base station side, the base station transmits the HARQ feedback by using a Physical Hybrid ARQ Indicator Channel (PHICH), a PDCCH, or an enhanced physical downlink control channel (EPDCCH).
However, for MTC UE in a coverage enhancement scenario, the MTC UE has a limited bandwidth capacity, and therefore the MTC UE cannot receive a PHICH and a PDCCH. Consequently, the PHICH and the PDCCH cannot be used in an ACK feedback or a NACK feedback for a PUSCH. If the base station adds the ACK/NACK feedback to an EPDCCH, the ACK/NACK feedback needs to be indicated by using one bit in downlink control information (DCI). However, system resource overheads are relatively high when the base station sends an ACK feedback or a NACK feedback for only one UE by using one EPDCCH, especially in the coverage enhancement scenario in which the DCI needs to be repeatedly used, resulting in extremely low system resource usage.